The Airbus A321 that crashed with 224 passengers onboard in Egypt’s Sinai Peninsula region, broke into two pieces mid-air, according to a Russian aviation expert.

Operated by Russia’s Kogalymavia airline, the airplane was flying to St Petersburg, Russia, from the Egyptian resort of Sharm El Sheikh,a popular tourist destination, when it crashed on Saturday.

All 224 people onboard were killed and the debris scattered over approximately 20km² in a mountainous region.

The plane was said to be flying at an altitude of 30,000ft.

While the Egyptian affiliate of Islamic State (IS), known as Sinai Province, claimed it brought down the plane, Russian authorities said the fatal accident happened because of a mechanical failure, although it was too early to figure out the reason.

IS claimed the plane was downed in response to Russia’s intervention in the Syrian war.

"The plane was said to be flying at an altitude of 30,000ft."

Although the authorities dismissed the terror group’s claim, several airlines are re-routing their flights to avoid Sinai.

The UAE, Qatar, Bahrain and Kuwait are changing the course of their flights. Lufthansa, Air France-KLM, Qatar Airways and Dubai-based Emirates and Fly Dubai airlines have re-routed their services.

The Egyptian government stated it was able to recover 163 bodies and transferred them to three facilities outside Sinai. The two black boxes of the aircraft have also been recovered.

Authorities said most of the passengers killed were Russian citizens, including 17 children, four Ukrainian nationals and one Belarusian.

Following the incident, four major international airlines and a regional carrier announced they will avoid flying over Sinai until the cause of the crash has been known by the investigators.

The crashed plane was built in 1997 and is one of the oldest A321s in service. It is the largest version of Airbus’s single-aisle family of jetliners.

Kogalymavia said the aircraft had undergone required maintenance checks. The A321 was repaired years ago after the tail strike in 2001.

Airbus said it logged nearly 21,000 flights and 56,000 flight hours.